The present invention relates in general to a jet weaving loom such as air jet loom and water jet loom, and more particularly to a weft pull-back device of such looms, which, prior to effecting the actual weft picking, pulls back the weft thread from the jet nozzle to reduce the length of the weft thread (or "dag") hanging out of the end of the nozzle in order to prevent the undesired tangling of the dag with the warp threads which would occur at the pre-jet operation of the nozzle.